Add option to provide ProtoOutputStream chunk size in newTracePacket

This is to avoid always allocating 8kb of memory on every single newTracePacket call, especially when we know the trace packet will be much smaller than this.

Bug: 372285118
Bug: 400413040
Flag: EXEMPT very minor bug fix
Change-Id: If7e1c4b3b241e2d4ffee66bf549faa8d2715cd77